Oil separator for refrigeration system



June

EVA PO RATOR 1956 R. c. WEBBER 2,749,723

OIL SEPARATOR FOR REFRIGERATION SYSTEM Filed Oct. 15, 1953 l2 RECEIVER I4 H547'EXCHANGE"? 52 COM PRES so R I N V EN TOR.

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United States Patent "ice OIL SEPARATOR FOR REFRIGERATION SYSTEM Robert C. Webber, Indianapolis, Ind.

Application October 15, 1953, Serial No. 386,307

2 Claims. (Cl. 62-117.75)

The present invention relates to refrigeration systems of the type utilizing a compressor for circulating the refrigerant and is particularly concerned with means for separating the oil from the refrigerant after it leaves the compressor and for returning such oil to the compressor crank case.

The primary object of the invention, is to provide an oil separator, for use in such a system, completely devoid of moving parts and from which the separated oil is continuously returned to the compressor crank case by bringing about an approximation between the rate at which the oil is separated from the refrigerant and the rate at which it is permitted to flow from the separator to the compressol.

,A further object is to provide means for removing a portion of the heat from the compressed refrigerant prior to its passage through the separator to facilitate the removal of the oil therefrom.

Another object is to provide means for cooling the separated oil prior to its return to the compressor crank case.

Further objects will become apparent as the description proceeds.

To the accomplishment of the above and related objects, my invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may be made in the specific construction illustrated and described, so long as the scope of the appended claims is not violated.

The single figure of the drawings is a more or less diagrammatic illustration of a conventional type of refrigeration system showing my invention incorporated therewith.

In the drawing, I have shown a compressor connected through a conduit 11 to the oil separator 12, constituting a part of my invention. From the separator 12, a conduit 13 connects to a receiver 14, preferably through a condenser 15, and from the receiver 14 a conduit 16 connects to the evaporator 17 through an expansion valve 18. A conduit 19 provides a return path for the refrigerant from the evaporator to the compressor.

Oil separators in general use heretofore have included a reservoir for the accumulation of the separated oil, and the return line for the oil to the compressor crank case has been dominated by some sort of a float-valve arrangement which permits intermittent return of the oil to the crank case. Such an arrangement is inherently subject to break downs and the need for repair, and, where the refrigeration system is located in a moving conveyance, the resultant vibrations render such a system highly unsatisfactory and ineflicient.

I have eliminated these difficulties by my invention, devoid of moving parts, in which I bring about an approximation between the rate at which the oil enters the separator and the rate at which it is permitted to leave the separator and return to the compressor crank case. My separator, as illustrated, comprises a body 20 having 2,749,723 Patented June 12, 1956 a chamber 21 formed therein. Intermediate the upper and lower ends of this chamber I provide a pair of perforated plates or screens 22 and 23, and between these plates I place a pad 24 of metallic wool. Such an arrangement divides the chamber 21 into upper and lower compartments 25 and 26, respectively. Conduit 11 is connected to conduct the oil-laden refrigerant to the lower compartment 26 through an inlet port 27, and conduit 13 is connected to conduct the separated refrigerant from the upper compartment 25, through outlet port 28, after passing through the filter pad 24. The separated oil flows from the filter pad to the bottom of compartment 26. A tube or conduit 29 connects said compartment to the crankcase of the compressor.

To bring about the desired approximation between the rate at which the oil enters and leaves the separator, I employ the resistance to liquid flow present in a tube of relatively small diameter. To this end I prefer to form the conduit 29 from tubing of relatively large diameter (for a purpose later to become apparent) and to insert intermediate the ends of this conduit, a further tube portion 30 of relatively small diameter. The diameter of tube 29 is such as to offer very little resistance to oil flow as compared to that of the portion 30. The diameter and length of tube portion 30 is such that the flow of oil therethrough is restricted to a degree sufiicient to maintain the rate of flow from the separator to the compressor substantially equal to the rate at which the oil is deposited in the separator.

The tube portion 30 must be comparatively long to obtain the desired resistance. I have found that I can effectively increase the restrictive effect of a given tube length by arranging it in a coil of relatively small diameter, as illustrated. For a given resistance, the required tube length can, thereby, be reduced substantially.

I have found from experimentation that for a given horsepower compressor the following internal diameters and lengths of the tube portion 30 are optimum in maintaining the desired rate of fiow:

I. D. Length A H. P. to l H. P .031 in. 84 in. 1 /2 H. P. to 3 H. P .031 in. 40 in. 5 H. P. to 10 H. P .050 in. 42 in. 15 H. P. to 30 H. P .127 in. 126 in. 40 H. P. to 50 H. P .127 in. 72 in. 60 H. P. to 75 H. P .127 in. 54 in. H. P .127 in. 40 in.

Where the internal diameter of the tube portion 30 is so small, it becomes necessary to maintain the oil relatively free from small bits of impurities and, for this reason, I prefer to provide, in most instances, an oil filter 31 connected in tube 29 between the separator 12 and the resistive tube portion 30, whereby such impurities will be removed before the oil reaches the small-diameter portion 39.

Where compressors of relatively high horse-power are used, I have found that the temperature of the compressed refrigerant is so high that etficient separation of the oil therefrom is impossible without reducing the temperature of the refrigerant somewhat before it enters the separator. To this end I prefer to provide, in some installations, a heat exchanger, referred to generally by the reference numeral 32, the conduit 11 being connected to conduct the refrigerant through this exchanger prior to its entrance into separator 12.

In such installations, I have found, too, that the temperature of the oil leaving the separator is still so high that its lubrication properties are greatly reduced, and that, in order to protect the compressor moving parts against improper lubrication, it is desirable to cool the oil prior to its return to the compressor crank case. I

therefore prefer to provide, in certain installations, cooler means 33, tube 29 being connected to conduct the returning oil through such cooler means.

My invention has a further advantage as a result of the fact that the return line for the oil to the crank case is never closed by a valve, or the like. When the compressor stops running, the pressure of the refrigerant in the separator 12 will force any remaining oil through tube 29 and the restricted portion 30 thereof into the compressor crank case. Thereafter, when the tube portion 30 is free of oil, refrigerant itself will bleed into the crank case, or low-pressure side of the system, thereby equalizing the pressure in the system. Any refrigerant which may have liquefied in separator 12 will be vaporized when passing through tube portion 30, thereby insuring against liquid refrigerant ever becoming mixed with the oil in the compressor crank case. Thus, when the compressor is again energized, there will be no load on the compressor as it comes up to speed. This is espe cially desirable in high-pressure systems where the ab sence .of some means for removing the load from the compressor during shutdown time would result in an overload on the compressor motor during starting periods.

My invention presents an extremely simple yet eflicient device for performing a function heretofore performed only by more elaborate and complicated mechanism. The fact that it contains no moving parts renders its use in any installation more trouble free and economical especially so where it is used in refrigeration systems located in moving conveyances.

I claim as my invention:

1. In a refrigeration system comprising a compressor having a crankcase, an inlet and a discharge, a condenser, conduit means for conducting compressed refrigerant from said compressor discharge to said condenser, an evaporator, conduit means for conducting condensed refrigerant from said condenser to said evaporator, and conduit means for conducting evaporated refrigerant from said evaporator to said compressor inlet, the invention of means for separating lubricant from the compressed refrigerant and for returning it to the compressor crankcase, such means comprising a body having a chamber therein, said first-named conduit means including a pipe communicating with said compressor discharge and entering said chamber and terminating in an open end within said chamber, and another pipe communicating with said condenser and entering said chamber and termimating in an open end within said chamber, filter means disposed in said chamber and interposed between the open ends of said pipes, and a continuously-open tube having one end disposed in said chamber below both said open pipe ends, extending upwardly through said chamber, and having its other end opening into said compressor crankcase.

2. The system of claim 1 in which at least a portion of said tube is of a restricted diameter such as to maintain the rate of flow of lubricant from said chamber to said crankcase substantially equal to the rate at which lubricant is deposited in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 346,038 Goldschmidt July 20, 1886 1,758,074 Davenport May 13, 1930 2,223,882 Beline Dec. 3, 1940 2,466,863 Phillips Apr. 12, 1949 2,512,758 Winkler June 27, 1950 2,606,430 Pownall Aug. 12, 1952 2,608,269 Briggs Aug. 26, 1952 2,614,402 Swart Oct. 21, 1952 

